Rat liver pp49, a protein that forms complexes with protein kinase CK2, is composed of the β and the γ subunits of translation initiation factor eIF-2

Comparison of the amino acid sequences of two peptides derived from proteolysis of rat liver pp49 identified it as composed of the β-subunit and the γ-subunit of eukaryotic initiation factor-2 (eIF-2). Partial purification of rat liver eIF-2 showed that its trimeric form (αβγ) co-eluted with protein kinase CK2. Heat-inactivated preparations of the trimeric form of eIF-2 inhibited CK2, increasing its Km for β-casein, as observed with pp49. The form of eIF-2 that lacks the β-subunit had no effect on CK2. These data indicate that the βγ subunits of eIF-2 may complex with CK2 and modulate its activity.